Over 11 years, the risk of developing diabetes was 32 percent higher among men who took Avodart and 26 percent higher among those who took Proscar, compared to those who took Flomax.

The study was published in the BMJ.

The increased risk of diabetes among men taking Avodart and Proscar is slight -- about an extra 16 cases for every 1,000 men treated over 10 years -- but it still a significant public health issue, according to study lead author Li Wei, associate professor, School of Pharmacy, University College London, U.K., The Times reported.

"We don't want anyone to suddenly change their drug," she said. "But you need to discuss it with a physician, especially if you are already at high risk for diabetes. You have to look at the overall picture of your condition in order to make a decision" about the best course of treatment."